Drawing of hollowware from sheet metal



Jan. 20, 1970 J. MARCOVITCH 3,490,265

DRAWING OF HOLLOWWARE FROM SHEET METAL Filed Aug. 11, 1967 5Sheets-Sheet 1 Jan. 20, 1970 J. MARCOVITCH DRAWING OF HOLLOWWARE FROMSHEET METAL s Sheets-Sheet 2' Filed Aug. 11, 1967 M9605 J/A/GCWV/ rayJan. 20, 1970 J covrrgH 3,490,265

DRAWING OF HOLLOWWARE FROM SHEET METAL Filed Aug. 11, 1967 3Sheets-Sheet 3 Arm s.

United States Patent 3,490,265 1 DRAWING 0F HOLLOWWARE FROM SHEET METALJacob Marcovitch, Johannesburg, Republic of South Africa, assignor toRotary Profile Anstalt, Vaduz, Liechtenstein Filed Aug. 11, 1967,Serf-No. 659,998 Claims priority, application Republic of South Africa,Aug. 19, 1966, 6614,959 Int. Cl. B21d 22/20, 22/22 U.S. Cl. 72-348 17Claims ABSTRACT OF THE DISCLOSURE Hollowware is deep drawn from metalsheet by clamping the peripheral zone of the sheet, applying drawingpressure to the central zone by a punch within a die, and simultaneouslyrolling the clamped peripheral zone betweentwo opposed series of smallrollers, arranged obliquely to the central zone, for-"matjerial to beurged from the peripheral zone towards the "central zone. The punch maybe rotatable and may have a series of small rollers roundit to roll thedrawn metal against the wall of the die.

This invention relates to the drawing of hollowware from sheet metal, inwhich the peripheral zone of the blank is clamped, while the unsupportedcentral zone is displaced, for instance, by a punch to produce thecomponent. I I

While this method of producing hollowware has obvious advantages overother techniques, suchas metal spinning, it imports its owndisadvantages. These are, principally, that the central zone has to beof sufiicient diameter in relation to the outer diameter of the blank,and that the blank-holder pressure must be verycn'tically regulated toproduce the article without rupture; and that the metal work-hardens,which means that the drawing operation must be suspended from time totime for the metal to be annealed. There is the further trouble that thesinking of the punch into the central zone tends to wrinkle the clampedrim.

The object of the present invention is to provide a drawing techniquewhich minimises the disadvantages and difiiculties of the conventionaldrawing methods.

According to the invention, the peripheral zone of the blank is clampedbetween two juxtaposed wheels of small rollers that are mounted forrotation about a common axis, the individual rollers 'beink skewlymounted to urge the material of the peripheral zone towards the axis ofrotation,

The concept upon which the invention proceeds is that the clamped rim isironed towards the central zone, while remaining clamped between the twoseries of rollers, so that it is progressively forced to maintain aconstant thickness, as the natural tendency for the rim is to thicken,or it may be thinned during the fironing, if this is desired, and thesurplus metal propelled inwardly into the central zone.

The central zone may be drawn in the conventional way by means of apunch, and, if it is, the flow of metal radially inwardly from theperipheral zone will facilitate the drawing operation, and lessen thenumber of annealing operations required. However, according to adevelopment of the invention, the drawing operation is associated with arolling operation, in which a series of rollers is presented to theinner wall of the drawn central area and rotates about the axis ofrotation of the punch. The rollers press against the inner wall andassist in the drawing operation, rolling out irregularities and wrinklesand assist- 3,490,265 Patented Jan. 20, 1970 ing to maintain the wallthickness uniform, if that is the desire, or to make the wall ofdifferent thicknesses. The inner rollers may be skewed to promote flowof metal downwardly into the drawing cavity and thus reduce the numberof annealing stages, while reducing frictional drag.

The technique of the invention is illustrated in the accompanyingdrawings, in which:

FIGURE 1 is a vertical section through one embodiment, the two wheels ofrollers are shown in section, clamping the rim of the blank betweenthem.

FIGURE 2 is a partial plan, and shows a fragmentary plan view of one ofthe wheels of rollers, the individual rollers being mounted with theiraxes of rotation at an acute angle to the radius of the wheel thatpasses through the centre of the roller. Each wheel is backed by solidstructure. The backing structures are rotated by means of suitable wormgearing and in opposite direction to neutralise torque on the component.

FIGURE 3 is a partial vertical section of a second embodiment.

The machine illustrated consists of a massive cylindrical base 10centrally apertured at 12 to form a drawing cavity of appropriatediameter. The base is recessed to accommodate a turret 14 that has aconical hole to mate with a conical spigot 16 on the base. The opposedconical faces, together with a cylindrical skirt 18 on the turret thatsurrounds the base, ensures that the turret rotate around the basewithout play. Rotation is assisted by providing a series of rollers 20between the opposed lateral faces of the base and the turret. The turretis driven around the base by a worm gear 21 that engages acircular rack23 formed in the outer surface of the turret.

The upper face of the turret is recessed at 22 to accommodate a wheelthat rotates freely around the spigot of the base. The wheel consists ofa fiat cage 24 which is extensively apertured, with a small roller 26mounted within each aperture. The rollers are skewed, as seen in FIGURE2, at an angle to the radii. The rollers need not be pinned to the cage,as they are supported on the floor provided by the turret.

A head 28 is mounted above the turret. It consists of a body 28 aroundwhich is arranged a cylindrical foot 30 that is formed centrally with aconical hole which receives a complemental spigot 32 on the body. Thefoot has an upstanding flange 34 that fits around a cylindrical part 36of the body. The two parts have a series of rollers 38 between them, andthe foot is rotated about the body by means of a worm gear 40 thatengages a circular rack 42 formedin the body. The two wheels of therollers are arranged for rotation in opposite directions.

The body is axially apertured slidably to receive a punch 44.

There is a second wheel mounted below the head. It, too, consists of aseries of rollers 46 mounted each' in a skewed aperture in a cage 48.The cage is troughshaped, and its rim 50' is curved to engage ashoulder52 on the foot 30. The rollers are held within the cage by means such aspins (not shown). The cage 48 is centrally apertured to pass the punch44.

The blank 54 to be worked on is a disc and is placed upon the wheel ofrollers 26, and the head is lowered for the wheel of rollers 46 to reston the blank. The punch 44 is then lowered and pressed downwardly todraw the central zone 56 of the blank. At the same time, the wheels ofrollers are caused to rotate by turning the worm gears 21 and 40. Therotation is in opposite directions, as stated above, in order toneutralise torque on the workpiece.

The alignment of the rollers is such that, as they rotate over and underthe peripheral zone of the workpiece,

they iron it out, and prevents the buckling which tends to occur as thedrawing proceeds. At the same time, the rollers, being skewed, causemetal to flow inwardly from the periphery inwardly towards the centre,thereby promoting uniformity in the thickness of the lands of thearticle, facilitating the drawing operation, and minimising the numberof annealings that will be required. The flow of metal radially inwardlyalso has the great advantage that it thickens the metal at the junction58 between the lands and the drawn part of the workpiece and permits adeeper draw than would otherwise be practicable.

The finished article is characterised by lands without buckles and offair uniformity of thickness. The rolling of the lands produces a highfinish, so that no aftertreatment is necessary.

In a further development of the invention, either the inner or outersurface of the component (or both) in the die is or are urged downwardlyduring the drawing operation by orbiting rollers lining the mouth of thedie for the walls of the punch. The punch is arranged for rotation.

This is shown in FIGURE 3, where the punch 44 carries a series of skewedrollers 62 held in a cylindrical cage 64 that is. fast with it. Thepunch is rotated to orbit the rollers .62. The punch is propelleddownwardly for the rollers 62 to draw the workpiece by rolling thecentral zone against the inner wall of the drawing cavity 12. Theskewing of the rollers 62 promotes flow of the material of the workpiecedownwardly into the cavity 12, thus assisting the drawing. The rollersroll out all irregularities and wrinkles and assist to produce a wall ofuniform thickness, or, if that be desired, a wall of dilferentthicknesses. A pad 70 is carried on the end of the punch and isseparated from the punch by a thrust bearing 72.

The provision of drawing rollers much reduces frictional drag, andminimises or avoids the need for annealing of the'drawn zone.

I claim:

1. Apparatus for drawing an article of hollowware from a sheet of metal,comprising a punch adapted todraw a central zone of the sheet, means tosupport the peripheral zone of the sheet surrounding the central zone,said means comprising, on at least one side of the sheet, a plurality ofrollers adapted to when the surface of the sheet, and means for forcingsaid rollers against said surface of the sheet in a direction to urgematerial from the peripheral zone of the sheet toward the central zone,each roller being skewed by having its axis inclined obliquely to a lineradial to the punch axis and intersecting the axis of the roller at thegeometric center of the roller, whereby roller rotation imparts spirallyinward forces to the sheet.

2. The apparatus of claim 1, and means mounting the rollers for movementrelative to the sheet in a path around the punch.

3. The apparatus of claim 1, in which the rollers are arranged withtheir axes parallel to the plane of the pe ripheral zone of the sheet.

4. The apparatus of claim 3, in which the rollers have substantiallycylindrical working surfaces.

5. A method of drawing an article of hollowware from a sheet of metal,comprising supporting a peripheral zone of the sheet against movementnormal to the plane of the sheet, applying pressure to a central zone ofthe sheet surrounded by the peripheral zone to draw the article, andforcing rollers against at least one surface of the sheet in theperipheral zone in a direction to urge the material of the peripheralzone toward the central zone with the roller axes inclined obliquely toa line radial to the punch axis and intersecting the axis of the rollerat the geometric center of the roller.

6. A method as claimed in claim 5, in which said forcing is elfected bymoving the rollers relative to the sheet in a path about said centralzone.

7. The method of claim 6, in which the rollers move in a circular patharound the cenral zone.

8. The method of claim 5, in which both surfaces of the sheet are rolledby rollers.

9. The method of claim 8, in which the direction of movement of therollers is different on opposite sides of the sheet.

10. The method of claim 9, in which the rollers on each side of thesheet move in a circular path around the central zone.

11. The method of claim 5, in which at least one surface of the centralzone is traversed by rollers while pressure is applied to the centralzone.

12. The apparatus'of claim 3, in which the rollers are supported in acage and backed in line contact by a wheel, the wheel being adapted tobe driven around the punch to cause the rollers to roll relatively onthe sheet.

13. The apparatus of claim 1, in which rollers and roller-mounting meansare provided on both sides of the sheet.

14. The apparatus of claim 13, in which the rollers on each side of thesheet have substantially cylindrical working surfaces and are arrangedwith their axes parallel to the plane of the peripheral zone of thesheet.

15. The apparatus of claim 13, in which the rollers on each side of thesheet are supported in a cage and backed in rolling contact by a wheel,and including means to drive the wheels in opposite directions.

16. The apparatus of claim 1, in which the punch is provided withrollers mounted at its surface for rotation and adapted to roll upon theinner surface of the drawn central zone of the sheet as drawingproceeds.

17. The apparatus of claim 16, in which the rollers are supported inrolling contact on the surface of the punch, the punch surface beingcircular in cross section, and including means to rotate the punchrelative to the central zone of the sheetas drawing proceeds.

References Cited UNITED STATES PATENTS 531,337 12/ 1894 Saltzkorn et al72350 2,988,208 6/1261 Loew 72-350 3,314,275 4/ 1967 Mullen 72---350FOREIGN PATENTS 87,874 8/ 1896 Germany. 98,092 2/ 1940 Sweden.

RICHARD J. HERBST, Primary Examiner U.S. Cl. X.R. 72-3 50

